It is generally known that the printing characteristics of a printing apparatus such as a color printer may change owing to environmental conditions such as the temperature and humidity of the environment in which the printing apparatus is being used. The condition of the environment is not the only factor. There are instances where printing characteristics change as a result of using the printer over a certain period of time. For example, in the case of an electrophotographic printer, there are instances where the photosensitivity characteristics of the photosensitive drum change owing to the aforementioned environmental conditions and due to aging with use, as a result of which printing characteristics such as tonality observed in printed images or the like change from what is desired. In the case of an ink-jet printer, it is known that a change in printing characteristics may occur owing to a change in the ink discharge characteristics of the printhead.
In general, a printer is calibrated to deal with the above-described changes in printing characteristics. In this case, a change in the printing characteristics of individual printers is not the only problem. An additional problem is that in an information processing system in which a plurality of printers are connected via a network, there is a difference in printing characteristics from one printer to another. Accordingly, not only is calibration of each individual printer required but it is also necessary to perform a calibration for the purpose of reducing variations in printing characteristics from one printer to another.
In the prior art, calibration of a printer fundamentally is carried out based upon a command input from a user. For example, when the user observes that the tonality of a printed image is not what is desired, the user commands execution of calibration using a control screen displayed on the printer or on a computer, etc., that is connected to the printer.
However, executing calibration of a printer often is troublesome and such calibration is a task that demands considerable user labor. For example, consider calibration of a printer in which image processing such as a luminance-to-density conversion and a gamma conversion is executed to finally acquire binary data and printing is carried out based upon this data. In order that the results of calibration executed with regard to a gamma correction table will be reflected in the printer in this case, an input of some kind is required at the printer based upon data obtained by the calibration. Making such an input is comparatively troublesome as far as the user is concerned.
Further, there are cases where separate operations are required regarding the printer and the computer connected to the printer in relation to a series of processes involved in execution of calibration, such as the printing and reading of patch data and entry of calibration data. Since these operations cannot be performed at one stroke, a great amount of labor is demanded of the user.
Furthermore, in an information processing system in which a plurality of printers are connected via a network, the above-described operations and processes involved in calibration must be performed a number of times equivalent to the number of connected printers. These operations and processes involved in calibration therefore complicate the user's task even more. Moreover, even if a single printer is shared by a plurality of computers, it is difficult for each user to execute calibration handily when necessary.